executor: improve usb coverage attribution
executor: improve usb coverage attribution

Always call write_extra_output() only if the current program or call
can produce extra coverage (== is a syz_usb* syzcall).

xairy/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller